Compared with man-made fibers, natural textiles, such as those made from cellulose and protein fibers, are much more vulnerable to microbe attack because of their hydrophilic porous structure and moisture transport characteristics. The use of antibacterial agents to prevent or retard the growth of bacteria on textile articles has been becoming a standard finishing method for textile goods, especially for those used in hospitals, hotels, sports and personal care industries. However, there is an increasing public concerns for possible effects of antibacterial finishing on environmental and biological systems. An ideal textile antibacterial finishing should not only kill undesirable microorganisms and stop the spread of diseases, but also be safe and environmentally benign. Furthermore, the antibacterial function should be maintained for as many cycles through a home laundering process as possible.
Obtained from the shells of crabs, shrimps and other crustaceans, chitosan (CTS) is a non-toxic, biodegradable and biocompatible natural polymer, and has long been used as a biopolymer and natural material in pharmaceutical, medical, papermaking and food processing industries. Because of its polycationic nature, chitosan possesses good antibacterial property against various bacteria and fungi. However, direct coating of chitosan onto textile articles has suffered from four major drawbacks:                1) Chitosan does not dissolve in water but instead only dissolve in acidic aqueous solution. Thus, a considerable amount of acid is used during the chitosan finishing process. This may cause many environmental problems due to the strong odor and corrosive property of acids.        2) The aqueous solution containing dissolved chitosan usually is quite viscous, thus the finishing process is difficult to handle.        3) Chitosan is a rigid material. It affects the fabric hand after coating.        4) Chitosan has strong water-absorption ability due to the presence of many polar groups. Thus the water-repellency of chitosan-treated textile goods is significantly reduced.        
Chitosan-containing particles with core-parts and shell-parts have been reported by Kuwahara et al in two U.S. patents (U.S. Pat. Nos. 6,359,032 and 6,252,003) used for other uses such as coloring and deodorizing agents. However, the chitosan molecules on the particle surface are not permanent due to the physical absorption property, thus can be easily released with environmental changes such as pH.
Thus at present, textiles with chitosan particles have not been able to adequately provide an antibacterial action of any permanence without considerable drawbacks.